The present disclosure relates to a method of designing a set of masks for a lithographic level, and more particularly to a method of decomposing shapes in a lithographic level into multiple sets of shapes corresponding to multiple lithographic masks, and an apparatus for implementing the same.
The ability to lithographically define shapes without the effect of corner rounding or other optical-proximity related effects is paramount as the features of semiconductor devices continue to shrink and as the overlay tolerance of lithographic tools and the ability of optical proximity correction to compensate for proximity effect are limited. For example, in a manufacturing scheme in which a “sea of fins” is first formed and unwanted portions of the fins are subsequently removed, the ability to form straight edges in the cut fins is critical in order to avoid formation of unwanted device features (such as deposition of unwanted semiconductor materials during a selective epitaxy process). Further, when the number of semiconductor fins needs to be reduced in order to provide devices having different on-currents, optical proximity effects can move the edge of a lithographically exposed and developed photoresist layer away from target locations and cause inclusion of an additional semiconductor fin or unwanted removal of a semiconductor fin. Thus, a method for printing a lithographic pattern with minimal impact due to optical proximity effects is desired.